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The Future of Medicine: AR Treats Phantom Limb Pain

Studies have shown that a good deal of amputees feel pain in their lost limbs, a condition known as Phantom Limb Pain (PLP). The condition is caused when the part of brain responsible for a limb’s movement becomes idle, and thus far has very difficult to treat. But a new study suggests therapy involving augmented reality and gaming could stimulate these unused areas of the brain, resulting in a significant reduction in discomfort.

Previous attempts to ease PLP by replicating sensory feedback from an artificial hand have included prosthetics and a treatment known as mirror therapy, where a reflection of the patient’s remaining limb is used to replace the phantom limb. Virtual reality systems have resulted in more sophisticated mirror therapy, but the approach is only useful for the treatment of one-sided amputees.

A research team from Sweden’s Chalmers University of Technology sought to overcome this and achieve greater levels of relief by testing a treatment where the virtual limb would be controlled through myoelectric activity. This is a process where the muscle signals which would control the phantom limb at the stump are detected and then used to create a pattern that will predict the limb’s movements and provide the requisite stimulation.

To test the treatment, the researchers connected amputee Ture Johanson – a man who have lived with PLP for 48 years – to a computer. Electrodes running from his stump to the machine provided the input signals, and on the computer screen, he was able to see and move a superimposed virtual arm. The electronic signals from his arm communicated to the computer and his movements were simulated before his very eyes, and then used to control a car in a racing game.

Within weeks of starting this augmented reality treatment in Max Ortiz Catalan’s clinic at Chalmers, his found his pain easing and even disappearing entirely. Mr Johanson says he has noticed other benefits, like how perceives his phantom hand to be in a resting, relaxed position rather than constantly a clenched fist:

The pain is much less now. I still have it often but it is shorter, for only a few seconds where before it was for minutes. And I now feel it only in my little finger and the top of my ring finger. Before it was from my wrist to my little finger… Can you imagine? For 48 years my hand was in a fist but after some weeks with this training I found that it was different. It was relaxed. It had opened.

Mr Johanson has also learned to control the movements of his phantom hand even when he is not wired up to the computer or watching the virtual limb.

Max Ortiz Catalan, the brains behind the new treatment, says giving the muscles a work-out while being able to watch the actions carried out may be key to the therapy. Catalan says it could also be used as a rehabilitation aid for people who have had a stroke or those with spinal cord injuries. As he put it:

The motor areas in the brain needed for movement of the amputated arm are reactivated, and the patient obtains visual feedback that tricks the brain into believing there is an arm executing such motor commands. He experiences himself as a whole, with the amputated arm back in place.

While he and his team points out that its research is based on the study of only one patient, the success in achieving pain relief following a series of unsuccessful treatments is a clear sign of efficacy and should lead to equally successful results in other test cases. Their research appeared in a recent issue of Frontiers in Neuroscience titled “Treatment of phantom limb pain (PLP) based on augmented reality and gaming controlled by myoelectric pattern recognition: a case study of a chronic PLP patient”.